Petroleum sulfonates are representative anionic surfactants which carry one or more sulfonate groups per molecule of sulfonated hydrocarbon. These petroleum sulfonates are useful in a variety of applications such as surfactant flooding in post-primary oil recovery operations. Increasingly important is the use of petroleum sulfonates for oil recovery. Some of the petroleum sulfonates can be used in micellar solutions having essentially zero interfacial tension with the oil to be recovered.
It is known to produce petroleum sulfonates by contacting a petroleum fraction with a sulfonating agent. A diluent may be present during this reaction. The reaction product comprises petroleum sulfonic acids, unreacted starting materials and diluent. The sulfonic acid moieties are normally neutralized to form the petroleum sulfonate and the diluent (when used) is removed.
A problem in the recovery of the petroleum sulfonates is the separation thereof from a reaction mass containing several other hydrophilic and oleophilic materials. It has been proposed in the art to achieve this separation by extracting the petroleum sulfonate containing mixture with an aqueous alcohol such as isopropanol.